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Synapses organize the brain by forming pathways that connect the parts of the brain governing everything we do—from breathing and sleeping to thinking and feeling. This is the essence of postnatal brain development, because at birth, very few synapses have been formed. The synapses present at birth are primarily those that govern our bodily functions such as heart rate, breathing, eating, and sleeping.
The development of synapses occurs at an astounding rate during children's early years, in response to the young child's experiences. At its peak, the cerebral cortex of a healthy toddler may create 2 million synapses per second (ZERO TO THREE, 2009). By the time children are 3, their brains have approximately 1,000 trillion synapses, many more than they will ever need.
Some of these synapses are strengthened and remain intact, but many are gradually discarded. This process of synapse elimination—or pruning—is a normal part of development. By the time children reach adolescence, about half of their synapses have been discarded; leaving the number they will have for most of the rest of their lives. Brain development continues throughout the lifespan. This allows us to continue to learn, remember, and adapt to new circumstances.
Two kinds of overproduction and pruning processes takes place. One is called experience-expectant because synapses are overproduced in certain parts of the brain during certain developmental periods awaiting (expecting) stimulation. For example during the first months of life, the brain expects visual and auditory stimulation. If normal range of sights and sounds occurs then the visual and auditory areas of the brain develop.
But the children who are born completely deaf receive no auditory stimulation and as a result the auditory processing area of their brains becomes devoted to processing visual information. Similarly, the visual processing area of the brain for the children blind from birth becomes devoted to auditory processing. Experience-expectant overproduction and pruning processes are responsible for general development in large areas of the brain and may explain why adults have difficulty with pronunciations that are not part of their native language. The neurons and synapses that are not involved in recognizing native language sounds may have been pruned, therefore learning these sounds as an adult requires intense instruction and practice.
Secondly is experience-dependent. Synaptic connections are formed based on the individuals’ experiences. New synapses are formed in response to neural activity in very localized areas of the brain when the individual is not successful in processing information. Again new synapses are produced than will be kept after pruning. Experience dependent processes are involved in individual learning such as mastering unfamiliar sound pronunciation in a second language studied.
Another important process that takes place in the developing brain is myelination. Myelin is the white fatty tissue that insulates mature brain cells by forming a sheath, thus ensuring clear transmission across synapses. This myelin coating makes message transmission faster and more efficient. Young children process information slowly because their brain cells lack the myelin necessary for fast, clear nerve impulse transmission (ZERO TO THREE, 2009). Like other neuronal growth processes, myelination begins in the primary motor and sensory areas (the brain stem and cortex) and gradually progresses to the higher-order regions that control thought, memories, and feelings. Also, like other neuronal growth processes, a child's experiences affect the rate and growth of myelination, which continues into young adulthood .Is also responsible for growth in brain size.
By the age of 3, a baby's brain has reached almost 90 percent of its adult size. The growth in each region of the brain largely depends on receiving stimulation, which spurs activity in that region. This stimulation provides the foundation for learning.
Lellah answered the question on August 4, 2021 at 11:25